¹Himela Moitra,^1,2Sumit Pathak,³Aditya K. Dagar,³R. P. Rajasekhar,^1,3Satadru Bhattacharya,¹Moumita Akuria,¹Saibal Gupta
Journal of Geophysical Research (Planets) (in Press) Open Access Link to Article [https://doi.org/10.1029/2023JE008206]
¹Department of Geology & Geophysics, Indian Institute of Technology Kharagpur, Kharagpur, WB, India
²Department of Geology, Faculty of Applied Sciences, Parul University, Vadodara, GJ, India
³Planetary Sciences Division, Space Applications Centre, Indian Space Research Organisation, Ahmedabad, GJ, India
Published by arramgement with John Wiley & Sons

Silicic lithologies on planetary surfaces indicate magmatic evolutionary processes in their interiors. The Wolf crater complex within Mare Nubium on the Moon is one such silicic construct associated with a high thorium anomaly. This study integrates morphological, compositional, chronological and gravity anomaly analyses of high-resolution data from various lunar missions to establish this construct as a silicic volcanic caldera. Lobate flows with steeply sloping fronts indicate that the crater rims comprise high-viscosity silicic lavas, while the structurally controlled inner crater walls suggest caldera collapse triggered by magma depletion. In the crater rims, low Christiansen Feature position values reaffirm the presence of silicic lithologies, consistent with the low gravity anomaly signature beneath the complex, while spectroscopic data reveal low mafic mineral abundances and negligible hydration features. Chronological analyses yield silicic volcanism ages coeval with surrounding mare basalts (3.8–3.6 Ga), while intra-caldera basalts have 2.36–2.02 Ga ages, indicating prolonged magmatism in this region. Melting of suitable crustal protoliths like alkali gabbronorite/monzogabbro/troctolite by basaltic underplating is inferred to have generated silicic magmas that formed the Wolf volcanic complex, instead of basaltic magma fractionation or silicate-liquid immiscibility processes. Large impacts during the Late Heavy Bombardment may have enhanced partial melting of the mantle and created crustal fractures that facilitated the ascent of viscous silicic melts through the lunar crust. Contemporaneous existence of suitable protoliths and adequate crustal pathways for magma ascent may have controlled silicic volcanism on the Moon, and can explain the sporadic occurrence and overlapping ages of the lunar silicic constructs.

¹Seamus L. Anderson et al. (>10)
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14268]
¹Space Science and Technology Centre, School of Earth and Planetary Sciences, Curtin University, Perth, Western Australia, Australia
Published by arrangement with John Wiley & Sons

Over the Nullarbor Plain in South Australia, the Desert Fireball Network detected a fireball on the night of June 1, 2019 (7:30 pm local time), and 6 weeks later recovered a single meteorite (42 g) named Arpu Kuilpu. This meteorite was then distributed to a consortium of collaborating institutions to be measured and analyzed by a number of methodologies including SEM-EDS, EPMA, ICP-MS, gamma-ray spectrometry, ideal gas pycnometry, magnetic susceptibility measurement, μCT, optical microscopy, and accelerator and noble gas mass spectrometry techniques. These analyses revealed that Arpu Kuilpu is an unbrecciated H5 ordinary chondrite, with minimal weathering (W0-1) and minimal shock (S2). The olivine and pyroxene mineral compositions (in mole%) are Fa: 19.2 ± 0.2 and Fs: 16.8 ± 0.2, further supporting the H5 type and class. The measured oxygen isotopes are also consistent with an H chondrite (δ17O‰ = 2.904 ± 0.177; δ18O‰ = 4.163 ± 0.336; Δ17O‰ = 0.740 ± 0.002). Ideal gas pycnometry measured bulk and grain densities of 3.66 ± 0.02 and 3.77 ± 0.02 g cm−3, respectively, yielding a porosity of 3.0% ± 0.7. The magnetic susceptibility of this meteorite is log χ = 5.16 ± 0.08. The most recent impact-related heating event experienced by Arpu Kuilpu was measured by 40Ar/39Ar chronology to be 4467 ± 16 Ma, while the cosmic ray exposure age is estimated to be between 6 and 8 Ma. The noble gas isotopes, radionuclides, and fireball observations all indicate that Arpu Kuilpu’s meteoroid was quite small (maximum radius of 10 cm, though more likely between 1 and 5 cm). Although this meteorite is a rather ordinary ordinary chondrite, its prior orbit resembled that of a Jupiter Family Comet (JFC) further lending support to the assertion that many cm- to m-sized objects on JFC orbits are asteroidal rather than cometary in origin.